The invention concerns a joining device for joining two workpieces comprising a stamp which can be moved up and down between a lower working position and an upper loading position, wherein a first workpiece and a second workpiece arranged under the first workpiece can be arranged between the stamp and the support table.
Joining devices of that kind include for example stroke embossing devices for the hot embossing of substrates, that is to say the at least partial application of a transfer layer of a hot embossing film to a substrate by means of the action of pressure and heat on the hot embossing film which rests on the substrate. In the stroke embossing method a hot embossing film is transferred onto the substrate by a heated embossing stamp of metal or silicone in a continuous up and down movement. In that case the form of the embossing stamp determines the shape of the embossing. The stroke embossing procedure is suitable inter alia for sharp-edged, positionally accurate application of individual hologram images or also for sharp-edged stamping out of and application of motifs with partial surface coverage.
It can advantageously be provided that the embossing force is locally varied in dependence on the configuration of the transfer layer to be transferred from the hot embossing film onto the substrate, in particular by virtue of locally different coverage on the part of the transfer layer. Different local embossing forces are possible for example by region-wise shims or by adjusting screws which make it possible to slightly tip an embossing head or a support table for the substrate to be embossed upon and thus to set different local embossing forces. A disadvantage is that the adjustment operation generally has to be effected manually directly at the embossing device in the immediate proximity of the heated embossing stamp and this is a tedious process because the local embossing forces cannot be directly measured and/or cannot be understood or can be only inadequately accurately understood and high apparatus conversion times are involved.
In addition the above-mentioned joining devices can include ultrasound and high frequency welding devices which are used for example to weld two workpieces of plastic together, such as for example automobile headlight housings or other multi-part plastic housings to be welded.